Interactive input systems that allow users to inject input (e.g. digital ink, mouse events, etc.) into an application program using an active pointer (eg. a pointer that emits light, sound or other signal), a passive pointer (eg. a finger, cylinder or other object) or other suitable input device such as for example, a mouse or trackball, are well known. These interactive input systems include but are not limited to: touch systems comprising touch panels employing analog resistive or machine vision technology to register pointer input such as those disclosed in U.S. Pat. Nos. 5,448,263; 6,141,000; 6,337,681; 6,747,636; 6,803,906; 7,232,986; 7,236,162; 7,274,356; and 7,532,206 assigned to SMART Technologies ULC of Calgary, Alberta, Canada, assignee of the subject application, the contents of which are incorporated by reference in their entirety; touch systems comprising touch panels employing electromagnetic, capacitive, acoustic or other technologies to register pointer input; tablet personal computers (PCs); laptop PCs; personal digital assistants (PDAs); and other similar devices.
Above-incorporated U.S. Pat. No. 6,803,906 to Morrison et al. discloses a touch system that employs machine vision to detect pointer interaction with a touch surface on which a computer-generated image is presented. A rectangular bezel or frame surrounds the touch surface and supports digital imaging devices at its corners. The digital imaging devices have overlapping fields of view that encompass and look generally across the touch surface. The digital imaging devices acquire images looking across the touch surface from different vantages and generate image data. Image data acquired by the digital imaging devices is processed by on-board digital signal processors to determine if a pointer exists in the captured image data. When it is determined that a pointer exists in the captured image data the digital signal processors convey pointer characteristic data to a master controller, which in turn processes the pointer characteristic data to determine the location of the pointer in (x,y) coordinates relative to the touch surface using triangulation. The pointer coordinates are conveyed to a computer executing one or more application programs. The computer uses the pointer coordinates to update the computer-generated image that is presented on the touch surface. Pointer contacts on the touch surface can therefore be recorded as writing or drawing or used to control execution of application programs executed by the computer.
Above-incorporated U.S. Pat. No. 7,232,986 to Worthington et al., discloses a camera-based touch system comprising a bezel that is illuminated by at least one light source, such as an array of infrared (IR) light emitting diodes (LEDs). Each light source is associated with and positioned adjacent each camera. The bezel reflects infrared light emitted by the at least one light source back towards the cameras. As a result, each camera sees a bright band of illumination within its field of view. When a pointer is positioned within the fields of view of the cameras, the pointer occludes the infrared illumination and therefore appears as a high-contrast dark region interrupting the bright band of illumination in each captured image allowing the existence of the pointer in captured images to be readily detected.
U.S. Patent Application Publication No. 2009/0058833 to Newton discloses an optical touch screen comprising a primary illumination source, a secondary illumination source and retro-reflective components positioned along the edge of the touch screen to reflect light, providing backlight to a light detection system. The primary illumination source (eg. a set of LEDs or diodes) emits light in a fan-shaped pattern with its apex aligned with the optical center of the detection system; while the secondary illumination source is not aligned with the optical center of the detection system. When an object is present, its position can be triangulated based on the direction of its shadow at the detection system.
U.S. Patent Application Publication No. 2009/0213093 to Bridger discloses an optical position sensing system including a plurality of radiation sources. The position of the radiation sources may be varied with respect to the aperture to achieve performance enhancement. Supplemental radiation sources may be positioned around the bezel so as to provide supplemental backlighting. Each of the plurality of supplemental radiation sources can be individually activated and deactivated, so as to selectively provide the supplemental backlighting to selected areas within the bezel.
U.S. Patent Application Publication No. 2009/0213094 to Bridger discloses an optical position sensing assembly including a body. An optical sensor is mounted to a rear face of the body and a radiation source is positioned within the body above the lens. A light path separator is positioned between the radiation source and an image window for the optical sensor, so that the radiation path is optically separated from the view path of the optical sensor.
Although the above-mentioned interactive input systems allow pointer contacts with the touch surfaces to be determined, in interactive input systems that employ retro-reflective material to return backlighting to imaging assemblies, a pointer may in certain circumstances cast a shadow that appears in captured image frames. Depending on the nature of the shadow, the shadow may be inadvertently detected as a pointer contact.
It is therefore an object of the present invention to provide a novel interactive input system and a novel method of reducing shadow pointer effects employed by the interactive input system.